Electronic device and control method of electronic device

ABSTRACT

An electronic device includes a tactile sensation providing unit  30  configured to provide a tactile sensation to a contact object being in contact with a panel  10  and a controller  50  configured to control the tactile sensation providing unit  30  based on an amount of change of data based on press to the panel  10.

CROSS REFERENCE TO RELATED APPLICATION

This application is a National Phase of International Application NumberPCT/JP2013/000113, filed Jan. 11, 2013, and claims priority to and thebenefit of Japanese Patent Application Nos. 2012-005560, 2012-005567 and2012-005571 filed on Jan. 13, 2012, the entire contents of which areincorporated herein by reference.

FIELD

The present invention relates to an electronic device and a controlmethod of an electronic device.

BACKGROUND

Recently, in electronic devices such as mobile phones, smartphones,tablet terminals, game machines, PCs (Personal Computers), electronicbooks, ATMs (Automated Teller Machines), automatic ticket vendingmachines, automatic vending machines, printers, copy machines, fax(facsimile) and the like, a growing number of electronic devices areequipped with a tactile sensation providing function that provides atactile sensation to the operator when he/she operates a panel (forexample, see Patent Literature 1).

CITATION LIST Patent Literature

PTL 1: The publication of Japanese Patent No. 4633167

SUMMARY OF INVENTION

The present invention is to provide an electronic device that mayimprove a tactile sensation providing function and may provide a tactilesensation appropriately without causing any discomfort to the operatorand a control method of the electronic device.

The electronic device according to the present invention to achieve theabove mentioned matter includes:

-   -   a tactile sensation providing unit configured to provide a        tactile sensation to a contact object being in contact with a        panel; and    -   a controller configured to control the tactile sensation        providing unit on the basis of amount of change of data based on        press to the panel.

The electronic device according to claim 1, in that the controllercontrols the tactile sensation providing unit based on a temporal amountof change of the data and a threshold of amount of change.

The controller calculates a vector indicating a temporal amount ofchange of the data and a polarity of the amount of change and controlsthe tactile sensation providing unit based on the vector and a thresholdvector.

The threshold vector has a press threshold vector in which the vectorcorresponds to a plus direction vector that indicates an increase in theamount of change and a release threshold vector in which the vectorcorresponds to a minus direction vector that indicates a decrease in theamount of change.

The absolute value of the press threshold vector is larger than that ofthe release threshold vector.

The controller controls the tactile sensation providing unit basedfurther on the data and a data threshold corresponding to the data.

Furthermore, a control method of the electronic device according to thepresent invention to achieve the above mentioned object is a controlmethod of an electronic device configured to control a tactile sensationproviding unit that provides a tactile sensation to a contact objectbeing in contact with a panel by a controller, the method includes astep of controlling the tactile sensation providing unit on the basis ofamount of change of data based on press to the panel.

Furthermore, the electronic device according to the present invention toachieve the above mentioned matter includes:

-   -   a tactile sensation providing unit configured to provide a        tactile sensation to a contact object being in contact with a        panel; and    -   a controller configured to control the tactile sensation        providing unit on the basis of amount of change of data based on        press to the panel and a threshold of amount of change, wherein    -   the controller changes, after the tactile sensation providing        unit provides a tactile sensation, the threshold of amount of        change.

The controller reduces, after the tactile sensation providing unitprovides a tactile sensation, the threshold of amount of change withtime.

The controller increases, after the tactile sensation providing unitprovides a tactile sensation, the threshold of amount of change withtime.

The controller changes, after the tactile sensation providing unitprovides a tactile sensation, the threshold of amount of changeaccording to the position of contact of the contact object to the panel.

Furthermore, a control method of an electronic device according to thepresent invention to achieve the above mentioned object is a controlmethod of an electronic device configured to control a tactile sensationproviding unit that provides a tactile sensation to a contact objectbeing in contact with a panel by a controller on the basis of amount ofchange of data based on press to the panel and a threshold of amount ofchange, the method includes a step of changing, after the tactilesensation providing unit provides a tactile sensation, the threshold ofamount of change.

Moreover, an electronic device according to the present invention toachieve the above mentioned matter includes:

-   -   a tactile sensation providing unit configured to provide a        tactile sensation to a contact object being in contact with a        panel; and    -   a controller configured to control the tactile sensation        providing unit on the basis of amount of change of data based on        press to the panel and a threshold of amount of change, wherein    -   the controller changes, after the tactile sensation providing        unit provides a tactile sensation, the threshold of amount of        change according to a maximum value of the data based on press        to the panel.

Furthermore, a control method of an electronic device according to thepresent invention to achieve the above mentioned matter is a controlmethod of an electronic device configured to control a tactile sensationproviding unit that provides a tactile sensation to a contact objectbeing in contact with a panel by a controller on the basis of amount ofchange of data based on press to the panel and a threshold of amount ofchange, the method includes a step of changing, after the tactilesensation providing unit provides a tactile sensation, the threshold ofamount of change according to a maximum value of the data based on pressto the panel.

According to the present invention, a tactile sensation providingfunction may be improved and a tactile sensation may be providedappropriately without causing any discomfort to the operator.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a schematic configuration of anelectronic device according to a first embodiment;

FIG. 2 is a certain partial circuit diagram relating to a piezoelectricelement in FIG. 1;

FIGS. 3A-3C are diagrams illustrating respectively an example of amounting structure of the electronic device in FIG. 1;

FIGS. 4A-4C are diagrams for explaining respectively a basicdetermination algorithm when a piezoelectric element is used as atactile sensation providing element and as a press detection element;

FIG. 5 is a diagram illustrating a certain change in an output voltageof the piezoelectric element based on the basic determination algorithmin FIG. 4;

FIG. 6 is a diagram illustrating, in the basic determination algorithmin FIG. 4, an example of a certain change in an output voltage of thepiezoelectric element when a release threshold voltage is set based on avoltage value after a charge discharge processing of the piezoelectricelement;

FIG. 7 is a schematic diagram schematically illustrating a vectorcalculated by a press/release determination unit in FIG. 1;

FIG. 8 is a diagram illustrating a change in an output voltage of thepiezoelectric element in a press pattern of “normal press/release”;

FIG. 9 is a diagram illustrating an example of a certain source code ofa vector determination portion of a press/release determination unit ofan electronic device according to a second embodiment;

FIG. 10 is a diagram illustrating a change in an output voltage of thepiezoelectric element in a press pattern of “hold”;

FIG. 11 is a diagram illustrating an example of a certain source code ofa change portion of a reference value of the press/release determinationunit of the electronic device according to the second embodiment;

FIG. 12 is a diagram illustrating an example of a certain source code ofthe change portion of the release threshold vector of the press/releasedetermination unit of the electronic device according to the secondembodiment;

FIG. 13 is a diagram illustrating a change in an output voltage of thepiezoelectric element in a press pattern of “normal press/release”; and

FIG. 14 is a diagram illustrating an example of a certain source code ofa change portion of a release threshold vector of a press/releasedetermination unit of an electronic device according to a thirdembodiment;

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will now be described withreference to the accompanying drawings.

(First Embodiment)

FIG. 1 is a block diagram illustrating a schematic configuration of anelectronic device according to a first embodiment of the presentinvention. The electronic device 1 illustrated in FIG. 1 has a panel 10,a display 20, a tactile sensation providing unit 30, a memory unit 40and a controller 50. The controller 50 has a press/release determinationunit 51 and a tactile sensation control unit 52.

The panel 10 is disposed normally on the front surface of the display20, and detects, on the operation face of the panel 10, contact orrelease of contact of a contact object (e.g. a finger or a stylus pen)to an object displayed on the display 20. In addition, the panel 10detects contact of a contact object to the operation face and supplies asignal according to the detected contact position to the controller 50.The panel 10 is configured using a known type, such as a resistive filmtype, a capacitive type and the like.

The display 20 is configured using, for example, a liquid crystaldisplay panel (LCD), an organic EL display panel and the like, iscontrolled by the controller 50 and displays objects such as characters,images, videos and the like.

The tactile sensation providing unit 30 is configured using, forexample, a piezoelectric element 31. The piezoelectric element 31 isdisposed on the backside of the panel 10, which is opposite theoperation face thereof, and generates vibration of a predeterminedvibration pattern in response to the drive signal (drive voltage)applied from the tactile sensation control unit 52. Thereby, thepiezoelectric element 31 provides a predetermined tactile sensation to acontact object being in contact with the operation face of the touchpanel 10.

Then, an output voltage (analog data) obtained from the piezoelectricelement 31 based on press to the panel 10 is supplied to thepress/release determination unit 51. That is, in the electronic device 1according to the present embodiment, the piezoelectric element 31 isused as a tactile sensation providing element and as a press detectionelement (a press detection element as an acceleration sensor, that is,an element that outputs a voltage in response to a pressure applyingvelocity or acceleration).

The memory unit 40 stores operation programs and various thresholds ofthe electronic device 1 in a nonvolatile manner, and various calculationresults and the like in a nonvolatile or volatile manner as well.

The controller 50 controls the entire operation of the electronic device1, and determines the processing to be executed based on the informationinput from the panel 10. The press/release determination unit 51 obtainsan output voltage from the piezoelectric element 31 based on press tothe panel 10, determines press or release based on the obtained outputvoltage, and supplies the determination result to the tactile sensationcontrol unit 52.

The tactile sensation control unit 52 applies a predetermined drivesignal to the piezoelectric element 31 based on the determination resultfrom the press/release determination unit 51. Thereby, the piezoelectricelement 31 provides a predetermined tactile sensation to a contactobject being in contact with the operation face of the panel 10.

FIG. 2 is an exemplified partial circuit diagram relating to thepiezoelectric element 31 in FIG. 1. One electrode (positive electrode)and the other electrode (negative electrode) of the piezoelectricelement 31 are connected to the tactile sensation control unit 52. Then,the positive electrode and the negative electrode of the piezoelectricelement 31 are connected to ADC (analog-digital converter) 80 viachangeover switches 61 and 62 and capacitors 71 and 72. In addition, theoutput from ADC 80 (data based on press (ADC value, digital data)) isinput to the press/release determination unit 51.

The tactile sensation control unit 52 includes step-up converters 521and 522, a positive electrode voltage control circuit 523 and a negativeelectrode voltage control circuit 524. The step-up converters 521 and522 increase an input voltage and generate a predetermined voltage. Thepositive electrode voltage control circuit 523 receives the voltagegenerated by the step-up converter 521 and generates a drive signal forpositive electrode under control of the controller 50. The generateddrive signal for positive electrode is applied to the positive electrodeof the piezoelectric element 31. Then, the negative electrode voltagecontrol circuit 524 receives the voltage generated by the step-upconverter 522 and generates a drive signal for negative electrode undercontrol of the controller 50. The generated drive signal for negativeelectrode is applied to the negative electrode of the piezoelectricelement 31.

Then, when the controller 50 causes the piezoelectric element 31 tofunction as a press detection element, it turns on the changeoverswitches 61 and 62. Thereby, the output voltage from the piezoelectricelement 31 passes through the capacitors 71 and 72, is converted intoADC value by ADC 80, and is supplied to the press/release determinationunit 51. Here, for the output voltage from the piezoelectric element 31,DC component thereof is cut by the capacitors 71 and 72, and only ACcomponent (fluctuation) is supplied to ADC80. ADC80 has, for example, anintermediate potential of about 1.5V, and with the intermediatepotential as a reference value (reference voltage), the potential on theinput side (the side of the capacitors 71 and 72) of ADC80 fluctuates.

In addition, when the controller 50 causes the piezoelectric element 31to function as a tactile sensation providing element, it turns off thechangeover switches 61 and 62 so that a drive signal applied to thepiezoelectric element 31 is not input to ADC80. In this state, accordingto the determination result by the press/release determination unit 51,the controller 50 causes the tactile sensation control unit 52 to applya drive signal for positive electrode to the positive electrode side ofthe piezoelectric element 31, and to apply a drive signal for negativeelectrode to the negative electrode side of the piezoelectric element31, thereby causing the piezoelectric element 31 to vibrate.

Here, for the drive signal for positive electrode and the drive signalfor negative electrode applied to the piezoelectric element 31, in orderto prevent the piezoelectric element 31 from being in a depolarizedstate, the minimum voltage of the drive signal for positive electrodeshould be equal to or more than the maximum voltage of the drive signalfor negative electrode. For example, when the withstand voltage of thepiezoelectric element 31 is 40V, the controller 50 causes, with theintermediate potential of 20V, the step-up converter 521 of the tactilesensation control unit 52 to increase the input voltage of 3.6V, forexample, to generate an output voltage of 40V, and causes the step-upconverter 522 to increase the input voltage of 3.6V to generate anoutput voltage of 20V.

Then the controller 50 causes the positive electrode voltage controlcircuit 523 to generate, for example, a half cycle sine wave drivesignal for positive electrode, with an amplitude of 20V to 40V, and toapply the generated drive signal for positive electrode to the positiveelectrode of the piezoelectric element 31. In addition, the controller50 causes the negative electrode voltage control circuit 524 to generatea half cycle inverse-phase sine wave drive signal for negativeelectrode, with an amplitude of 0V to 20V, and to apply the generateddrive signal for negative electrode to the negative electrode of thepiezoelectric element 31. Thereby, the piezoelectric element 31 providesa predetermined tactile sensation to a contact object being in contactwith the operation face of the panel 10. Note that the tactile sensationcontrol unit 52 may, as long as within a range in which nodepolarization of the piezoelectric element 31 occurs, apply a voltagethat is lower than that for the negative electrode to the positiveelectrode.

FIGS. 3A-3C illustrate an example of a mounting structure of theelectronic device 1 illustrated in FIG. 1. FIG. 3A is an appearanceperspective view. FIG. 3B is a schematic cross sectional view taken fromline B-B in FIG. 3A. FIG. 3C is a plan view of the main part. Theelectronic device 1 illustrated in FIG. 3 is what is called asmartphone. The display 20 is enclosed and held in a housing 11. Thepanel 10 is held above the display 20 via an insulator 12 made of anelastic member. The panel 10 is held above the display 20 via insulators12 provided respectively at the four corners, away from a display regionA of the display 20 illustrated in FIG. 3C by phantom lines.

In addition, in the housing 11, an upper cover 13 is provided so as tocover a surface region of the panel 10, which is away from the displayregion of the display 20. An insulator 14 made of an elastic member isprovided between the upper cover 13 and the panel 10.

Note that, for the panel 10 illustrated in FIG. 3, the surface memberhaving an operation face (surface) 10 a is made of, for example,transparent film or glass, and the back side member having a back face10 b is made of glass or acrylic. The panel 10 is configured so that,when its operation face 10 a is pressed, the pressed portion thereofbends (strains) slightly or the structure itself bends slightlyaccording to the pressing force.

On the back side 10 b of the panel 10, piezoelectric vibrators 31 tovibrate the panel 10 are provided respectively, via adhesive or thelike, near each of two opposing sides. The two piezoelectric vibrators31 are driven in parallel or independently, thereby causing the panel 10to vibrate, and the operation face 10 a vibrates. Note that, in FIG. 3C,the housing 11, the upper cover 13 and the insulator 14 illustrated inFIG. 3B are omitted.

Here, the algorithm for determining press/release of the contact objectto/from the panel 10 is discussed. FIGS. 4A-4C are diagrams illustratinga basic determination algorithm when the piezoelectric element 31 isused as a tactile sensation providing element and as a press detectionelement. FIG. 4A is a timing chart illustrating a discharge timing ofthe piezoelectric element 31. FIG. 4B is a timing chart illustrating adrive timing of the piezoelectric element 31. FIG. 4C is a diagramillustrating an output voltage from the piezoelectric element 31supplied to the input side of ADC 80. In this determination algorithm,first, the controller 50 causes the piezoelectric element 31 to functionas a press detection element. Then, in the press/release determinationunit 51, when the output voltage from the piezoelectric element 31 basedon press of a contact object to the panel 10 by the operator reaches thethreshold voltage (R₀) and is determined as press, the controller 50causes the piezoelectric element 31 to function as a tactile sensationproviding element. Thereby, the tactile sensation control unit 52 drivesthe piezoelectric element 31 and provides a tactile sensation to theoperator. Then, after the piezoelectric element 31 is driven, in orderto restore the output voltage from the piezoelectric element 31 to thereference voltage, the controller 50 executes processing of dischargingthe charge of the piezoelectric element 31 in the discharge circuit(charge discharge processing).

After that, the controller 50 causes the piezoelectric element 31 tofunction as a press detection element, and when the operator removes thecontact object from the panel 10 (release), the output voltage from thepiezoelectric element 31 changes from the reference voltage to the minusdirection. In the press/release determination unit 51, when the outputvoltage from the piezoelectric element 31 reaches the threshold voltage(R₁) and is determined as release, the controller 50 causes thepiezoelectric element 31 to function as a tactile sensation providingelement, and causes the tactile sensation control unit 52 to drive thepiezoelectric element 31. Thereby, the piezoelectric element 31 providesa tactile sensation to the operator. Then, after driving thepiezoelectric element 31, in order to restore the output voltage fromthe piezoelectric element 31 to the reference voltage, the controller 50executes charge discharge processing of the piezoelectric element 31 tobe prepared for the next determination operation.

FIG. 5 is a diagram illustrating a certain change in the output voltagefrom the piezoelectric element 31 based on the basic determinationalgorithm illustrated in FIG. 4. Here, the reference voltage is 1.6V. Inthe basic determination algorithm, for example, a threshold voltage fordetermining that press has been performed (hereinafter referred to as apress threshold voltage) and a threshold voltage for determining thatrelease has been performed (hereinafter referred to as a releasethreshold voltage) are set respectively. Then, the press/releasedetermination unit 51 determines, when the obtained output voltage value(ADC value) is more than the press threshold voltage (data threshold),that press has been performed, and when the obtained output voltagevalue is less than the release threshold voltage (data threshold), thatrelease has been performed. In this case, it is assumed that the releasethreshold voltage is set lower than the reference voltage.

However, when the piezoelectric element 31 functions as a pressdetection element, it detects acceleration of depression (pressacceleration). In this case, the piezoelectric element 31 has acharacteristic in that it naturally discharges the charge accumulated bybending if there is no change in bending of the piezoelectric element31. Therefore, when a contact object such as a finger is released fromthe panel 10, if the contact object is released slowly and not quickly,that is, the contact object is released in a manner of press pattern of,what is called a “slow release,” a voltage lower than the referencevoltage may not be detected from the piezoelectric element 31. As aresult thereof, even if the contact object is released from the panel 10before the output voltage reaches the release threshold voltage, it maybe determined as a press state being kept.

As a method of solving such an inconvenience, it is assumed that arelease threshold voltage is set based on the voltage value after thecharge discharge processing of the piezoelectric element 31 (after thetactile sensation providing unit provides a tactile sensation). Thereby,even if the contact object is released from the panel 10 slowly, releasemay be determined FIG. 6 is a diagram illustrating an example of acertain change in the output voltage from the piezoelectric element 31in this case. Although FIG. 6 illustrates a case where the releasethreshold voltage is set higher than the reference voltage, the releasethreshold voltage may be set lower than the reference voltage. Here, thereference voltage is 1.5V. Note that, in FIG. 6, as described later, thepress/release determination unit 51 determines the case where theobtained output voltage value is less than the release threshold voltageand the absolute value of the amount of change (negative amount ofchange) of the output voltage value satisfies (is more than) theabsolute value of the release threshold vector (threshold of amount ofchange) as “release.”

Also, the investors observed that, through their diligent experimentsand examinations, in press/release, it is not always the case that theoutput voltage from the piezoelectric element 31 will take the waveformas illustrated in FIG. 6, and depending on the pressing state and thelike by the operator, the waveform changes every time. For example, theinventors have found that the voltage value detected for the first timeafter the charge discharge processing, the amount of change and thedirection of the change (positive or negative change) of the voltagedetected after the charge discharge processing vary in each chargedischarge processing. Thus, an accurate determination of press/releasemay be difficult.

Therefore, in the electronic device 1 according to the presentembodiment, a press threshold voltage as well as a release thresholdvoltage are set based on the voltage value after the charge dischargeprocessing of the piezoelectric element 31 (ADC value obtained by thepress/release determination unit 51). The press threshold voltage (inthe case where a plurality of press threshold voltages are provided, andas a press to the panel 10 is increased, input at a plurality of stagesmay be accepted based on the plurality of press threshold voltages, forexample, the press threshold voltage at the second stage) is set, forexample, if a tactile sensation providing operation is not executed forover a predetermined period of time and the output voltage is thereference value, to an initial threshold voltage that is higher than thereference value by a predetermined voltage. In addition, after a tactilesensation providing operation is executed, within a predetermined periodof time after the latest provision of a tactile sensation, a pressthreshold voltage is set based on the output voltage in thepredetermined period of time. In this case, for example, the pressthreshold voltage is set to a value obtained by adding a predeterminedvoltage to is the output voltage at the point in time when a certainperiod of time has elapsed from provision of a tactile sensation by thetactile sensation providing unit (from the start of the tactilesensation providing processing or the end thereof), or from the chargedischarge processing (from the start of the charge discharge processingor the end thereof) plus a predetermined voltage. Note that, in thiscase, a press threshold voltage may not be set before elapse of thecertain period of time, and whatever the ADC value the press/releasedetermination unit 51 obtains, it may not be determined as “press.”Also, the press threshold voltage may be set, for example, based on anoutput voltage after a tactile sensation is provided to the latest press(or after the charge discharge processing after provision of a tactilesensation) (the output voltage (ADC value) detected for the first timeby the press/release determination unit 51), to the voltage value thatis higher than the output voltage by a predetermined voltage.

Next, the release threshold voltage is set, for example, to a valueobtained by subtracting a predetermined voltage from the output voltageat the point in time when a certain period of time has elapsed from, forexample, provision of a tactile sensation by the tactile sensationproviding unit (from the start of the tactile sensation providingprocessing or the end thereof), or from the charge discharge processing(from the start of the charge discharge processing or the end thereof).In addition, the release threshold voltage may be set, based on anoutput voltage after the latest provision of a tactile sensation (orafter the charge discharge processing after the provision of a tactilesensation) (the output voltage value (ADC value) detected for the firsttime by the press/release determination unit 51), to the voltage valuethat is lower than the output voltage by a predetermined voltage.Thereby, the press threshold voltage and the release threshold voltageare changed and set each time the tactile sensation providing unitprovides a tactile sensation.

Note that, as described above, the piezoelectric element 31 has acharacteristic in that, it naturally discharges charge accumulated dueto bending, thereby, even if the contact object is released from thepanel 10 after it is pressed against the panel, the output voltage lowerthan the reference voltage may not be detected from the piezoelectricelement 31. Therefore, as described above, if the release thresholdvoltage is lower than the reference voltage when it is set to the abovedescribed value, that is, the value of the output voltage at the pointin time when a certain period of time has elapsed minus a predeterminedvoltage, it may be set to a predetermined voltage (e.g. a voltage higherthan the reference voltage by a predetermined voltage).

Note that, as described above, in press/release, the output voltage fromthe piezoelectric element 31 may not always take the waveformillustrated in FIG. 6, and the waveform may change significantly eachtime depending on the press condition of the operator and the like.Therefore, in the electronic device 1, in order to reduce thepossibility that the output voltage from the piezoelectric element 31exceeds the press threshold voltage or falls below the release thresholdvoltage without operator's intention, the press threshold voltage andthe release threshold voltage may be set based on the amount of changein the output voltage after the charge discharge processing (afterprovision of a tactile sensation). For example, when a press thresholdvoltage is set to a value, which is the output voltage at the point intime when a certain period of time has elapsed plus a predeterminedvoltage, if the absolute value of the amount of change in the outputvoltage after the charge discharge processing is large, thepredetermined voltage may be set to a large value, and if the absolutevalue thereof is small, the predetermined voltage may be set to a smallvalue. Similarly, when the release threshold voltage is set to a value,which is the output voltage at the point in time when the certain periodof time has elapsed minus a predetermined voltage, if the absolute valueof the amount of change of the output voltage after the charge dischargeprocessing is large, the predetermined voltage may be set to a largevalue, and if the absolute value thereof is small, the predeterminedvoltage may be set to a small value.

Furthermore, in the electronic device 1 according to the presentembodiment, not only the press threshold voltage and the releasethreshold voltage, that is, the fixed threshold voltage (data threshold)corresponding directly to the output voltage value of the piezoelectricelement 31, but also the threshold vector corresponding to the change inoutput voltage are used. Thereby, in the press/release determinationunit 51, ADC value is obtained from ADC 80, and from the obtained ADCvalue, as schematically illustrated in FIG. 7, a vector indicating atemporal amount of change in ADC value and the polarity of the amount ofchange is calculated as well.

Then, the press/release determination unit 51 compares the obtained ADCvalue with the press threshold voltage and the release thresholdvoltage, which are data threshold stored in the memory unit 40, andcompares the calculated vector with the press threshold vector and therelease threshold vector stored in the memory unit 40 as well.

As a result thereof, if the calculated vector is a plus direction vectorindicating an increase in the amount of change, and its absolute value(amount of change) satisfies the absolute value of the press thresholdvector (threshold of amount of change) a predetermined number of timesin the press/release determination processing performed, for example,every 2 ms (e.g. if the absolute value of plus direction vector islarger than the absolute value of the press threshold vector, it isdetermined as “satisfied”), and the obtained ADC value satisfies thepress threshold voltage as well, the press/release determination unit 51determines it as “press.” Then, if the calculated vector is a minusdirection vector indicating a decrease in the amount of change, and itsabsolute value (amount of change) satisfies the absolute value of therelease threshold vector (threshold of amount of change) a predeterminednumber of times in the press/release determination processing performed,for example, every 2 ms (e.g. if the absolute value of minus directionvector is larger than the absolute value of the release thresholdvector, it is determined as “satisfied”), and the obtained ADC valuesatisfies the release threshold voltage as well, the press/releasedetermination unit 51 determines it as “release.” The determinationresult of press/release by the press/release determination unit 51 issupplied to the tactile sensation control unit 52.

Here, the calculation of vector and the press/release determinationprocessing by the press/release determination unit 51 are executed, forexample, every 2 ms by using the average value calculated from the ADCvalues, that are obtained 10 times for about 40 μs. Then, the absolutevalue of the press threshold vector used for the determination of pressis set larger than that of the release threshold vector used for thedetermination of release. That is, when pressing, if a force iscontinued to be applied, the ADC value continues to rise until itbecomes physically impossible to rise, however, when releasing, if acontact object is released, it is impossible to decrease the ACD valueany more. Thus, if the absolute value of the release threshold vector isset to the same value as that of the press threshold vector, it is morelikely to cause a “withheld release” (a phenomenon in which even if acontact object is released, release vibration may not be generated).Thereby, for the release threshold vector, the conditions are eased(e.g. the absolute value of the release threshold vector is set smallerthan that of the press threshold vector) to allow easy determination ofrelease. In addition, for the release threshold vector, when the releasethreshold voltage is set to the value closer to the reference value, theabsolute value is set smaller than the case where the value is set farfrom the reference value to allow easy determination of release.

Furthermore, for the press threshold vector, when the press thresholdvoltage is set to the value which is far from the reference value, theabsolute value thereof may be set smaller than the case where it is setto the value which is close to the reference value. Although thepiezoelectric element 31 outputs a voltage when it is pressed anddeformed, with an increasing amount of deformation thereof, its elasticforce increases, thereby hardly be deformed. Therefore, in thepiezoelectric element 31, when the amount of deformation increases andoutput voltage becomes large, in order to change the output voltagefurther, a larger force is required compared to the case where theoutput voltage is small. Therefore, as described above, for the pressthreshold vector, when the press threshold voltage is set to a valuewhich is far from the reference value, the absolute value thereof is setsmaller than the case where the value is set close to the referencevalue, thereby improving the user operability whether the pressthreshold voltage is far from or close to the reference value.

In addition, when the press/release determination unit 51 performs, asdescribed above, the press/release determination processing at intervalsof a predetermined period of time, and determines “press/release” whenit determines that the absolute value of the vector of the outputvoltage (ADC value) from the piezoelectric element 31 is larger than theabsolute value of the press/release threshold vector a predeterminedtimes in a row, the absolute value of the press/release threshold vectormay gradually be decreased with each press/release determinationprocessing. Since the piezoelectric element 31 has a characteristic inthat it naturally discharges the charge accumulated due to bending, evenif the bending state is kept, the output voltage becomes small withtime. With such decrease in the output voltage with time in mind, theabsolute value of the press/release threshold vector may be decreasedgradually each time the press/release determination processing isperformed.

In the tactile sensation control unit 52, according to the determinationresult from the press/release determination unit 51, a predetermineddrive signal is applied to the piezoelectric element 31. Thereby atactile sensation is provided to the operator who presses the panel 10.

According to the electronic device 1 of the above described embodiment,the output voltage (ADC value) from the piezoelectric element 31 isobtained and a vector indicating the temporal amount of change in theoutput voltage and the polarity of the amount of change is calculated aswell, thus a waveform of the output voltage caused by fluctuation of thecontact object that is pressed/released by the operator may berecognized. Therefore, the press state and the release state may berecognized by comparing the vector with the threshold vector, therebyallowing a reliable determination of press/release for which a tactilesensation is provided, even in the case of multistage press/release.Therefore, a tactile sensation providing function may be improved and atactile sensation may be provided appropriately without causing anydiscomfort to the operator.

(Second Embodiment)

The press pattern of the panel 10 by the operator includes four patternssuch as, for example, “normal press/release, ” “repeated strikes, ”“hold” and “slow release.” The “repeated strikes” is a press pattern bywhich press and release are consecutively repeated in a short period oftime. The “hold” is a press pattern by which, release is performed notimmediately after press, and the press state is held for a while, andthen release is performed, which is so called a “long press.” The “slowrelease” is a press pattern by which, as described above, when releaseis performed, the contact object is released from the panel 10 notimmediately, but slowly. The “normal press/release” is a common presspattern belonging to none of the above described three patterns, and isa press pattern by which the panel 10 is pressed and is immediatelyreleased.

In the case of “normal press/release,” as described above, according tothe determination result from the press/release determination unit 51,the piezoelectric element 31 is driven by the tactile sensation controlunit 52, and the output voltage from the piezoelectric element 31changes, for example, as illustrated in FIG. 8. Note that, in FIG. 8,for convenience sake, the vertical axis represents ADC value by ADC 80.ADC value is “0” at a minimum, “65520” at a maximum, and the referencevalue (reference voltage of 1.5V) is around the middle, which is“32760.”

As illustrated in FIG. 8, in the case of “normal press/release,” forexample, after the piezoelectric element 31 discharges its charge afterpress vibration, ADC value rises sharply from the value that is equal toor less than the reference value. Then, after the piezoelectric element31 discharges its charge immediately after the release vibration, forexample, ADC value rises sharply and then rises slowly toward the valuewhich is slightly larger than the reference value. Thereby, if theabsolute value of the press threshold vector is set in a fixed manner,the vector after provision of a press/release tactile sensationsatisfies the press threshold vector and may be determined erroneouslyas press.

Thereby, in the electronic device according to the second embodiment ofthe present invention, in the electronic device 1 according to the firstembodiment, after the piezoelectric element 31 provides a press/releasetactile sensation, further, in the press/release determination unit 51,control is made so that the threshold vector for press/releasedetermination is changed. In detail, in the output voltage waveform asillustrated in FIG. 8, in order to prevent the sharp rise in the voltageafter provision of a tactile sensation from being determined as press,the absolute value of the press threshold vector is set largerimmediately after the start of calculation of vector after provision ofa tactile sensation, then is decreased with time.

FIG. 9 illustrates an example of certain source code of vectordetermination portion in the press/release determination unit 51 in thiscase. The variables illustrated in FIG. 9 are as follows:

-   -   “pre_ave_power”: ADC value obtained when the previous vector is        determined;    -   “ave_power”: ADC value obtained when the present vector is        determined;    -   “rel_vect”: Absolute value of release threshold vector;    -   “tilt”: Direction of vector [TILT_NONE: No change, TILT_MINUS:        Minus direction, TILT_PLUS: Plus direction];    -   “vect_pow”: The value “100” is assigned immediately after press,        and the value is decreased by “1” until it becomes “0”each time        a vector is determined;    -   “user_calibration.a_fn”: Value for in-plane calibration in        response to the contact position on the panel 10; and    -   “up_times”: The number of times a plus direction vector is        generated consecutively.

In FIG. 9, “else if (pre_ave_power>=(ave_power+rel_vect))” indicates thedetermination portion of minus direction vector. Then, the “else if(pre_ave_power<=(ave_power−0×3*vect_pow−(user_calibration.a_fn*2/up_times)))”indicates the determination portion of plus direction vector, and“vect_pow” prevents the sharp rise in voltage immediately afterprovision of a tactile sensation from being determined erroneously aspress.

Then, when the press pattern is “hold,” the output voltage from thepiezoelectric element 31 changes, for example, as illustrated in FIG.10. The change in the output voltage in this case is basically the sameas that of the “normal press/release.” However, even while the pressingforce is kept after press, ADC value declines gently. Thereby, if therelease threshold vector is set in a fixed manner, it may be determinederroneously as release.

Furthermore, after release vibration, for example, ADC value declinesonce, and restores slowly from the value that is significantly lowerthan the reference value to the reference value at a low speed. Thus,when a multistage press/release processing of two or more stages isperformed in the same region of the panel 10, the width of ADC valuerequired for ADC value to reach the press threshold voltage for the nextpress becomes wider than the normal one, which increases a forcerequired for press, thereby causing discomfort to the operator.

Then, in the electronic device 1 according to the present embodiment, inthe press/release determination unit 51, when the press pattern is“hold,” the absolute value of the release threshold vector afterprovision of a tactile sensation is further increased with time. Theactual source code in this case is “else if(pre_ave_power>=(ave_power+rel_vect))” in FIG. 9, in which “rel_vect” isa value by which a decline during “hold” is not regarded as release.Note that, the voltage decline rate of the piezoelectric element 31varies depending on the pressed position on the panel 10, thereby thevalue of “rel_vect” is changed by “ser_calibration.a_fn” depending onthe pressed position.

Furthermore, the press/release determination unit 51 sets, when itchanges the setting of the press threshold voltage based on the voltagevalue after the charge discharge processing of the piezoelectric element31, the ADC value at the point in time when a predetermined period oftime has elapsed from provision of a release tactile sensation, that is,the ADC value at the point in time when a predetermined period of timehas elapsed from the start of obtaining the ADC value after provision ofa release tactile sensation, as a reference value. Then, thepress/release determination unit 51 changes the press threshold voltageso that the difference from the reference value will be a constantvalue, in accordance with the reference value that has been set.

FIG. 11 is a diagram illustrating an example of a certain source code ofthe changed portion of the reference value in the press/releasedetermination unit 51 in this case. Then, FIG. 12 is a diagramillustrating an example of a certain source code of the changed portionof the release threshold vector. Variables indicated newly in FIGS. 11and 12 are as follows:

-   -   “getV”: Obtained ADC value;    -   “base_getV”: ADC value which will be a reference (reference        value). The press threshold voltage varies based on the        difference from the reference value. The default value is        “0×FFFF.”    -   “update_times”: The number of times a press/release        determination is performed after provision of a tactile        sensation. The press/release determination is performed every 2        ms;    -   “down_thresh”: The number of consecutive times the minus        direction vector is detected to be determined as release.

FIG. 11 illustrates a case where the ADC value after 16 ms from thestart of obtaining ADC value after provision of a release tactilesensation is set as a reference value. Then, FIG. 12 illustrates a casewhere, when the time period from the press (value of update_times) is acertain value or more, the press is regarded as “hold,” and the value ofthe release threshold vector (rel_vect) increases with time. Inaddition, in FIG. 12, the position where the value of“user_calibration.a_fn” is less than “12” represents the position wherea voltage is not detected appropriately, such as corners of the panel10. On such positions, compared with the center of the panel 10, thevalue restores to the reference voltage sooner, and the decline rate ishigh, thereby the release threshold vector is set to a larger value.Furthermore, compared with the center of the panel 10, on the positionwhere voltage is not detected appropriately such as corners of the panel10, the value of the press threshold vector may be set to a smallervalue.

According to the electronic device 1 of the present embodiment describedabove, the threshold vector after provision of a tactile sensation ischanged with time according to the press pattern, thereby, in additionto the effect by the first embodiment, in the press pattern of “normalpress/release,” a sharp rise in the absolute value of the plus directionvector after provision of a tactile sensation may be prevented frombeing determined erroneously as “press.” In addition, in the presspattern of “hold,” the hold state of pressing force may be preventedfrom being determined erroneously as “release.”

(Third Embodiment)

On the other hand, in the configuration illustrated in FIG. 2, theoutput voltage of the piezoelectric element 31 detected by ADC 80depends on the capacity of capacitors 71 and 72 connected to the inputside of ADC 80, and when the capacity is small (e.g. 1 μF), comparedwith the case where the capacity is large (e.g. 10 μF), time constant issmall, and less time is required to restore to the reference voltage. Inthe electronic device 1 according to the present embodiment, thecapacity of capacitors 71 and 72 is small such as, for example, 1 μF.

In this case, for example, in the normal press/release operation bywhich the panel 10 is pressed and then released immediately andcontinuous press, as described above, when the piezoelectric element 31is driven by the tactile sensation control unit 52 based on thedetermination result from the press/release determination unit 51, theoutput voltage from the piezoelectric element 31 changes, for example,as illustrated in FIG. 13. FIG. 13 illustrates change in the outputvoltage in the press pattern of “normal press/release.” In addition, inFIG. 13, for convenience sake, output voltage is represented as ADCvalue by ADC 80 on the vertical axis. ADC value is “0” at a minimum,“65520” at a maximum, and the reference value (reference voltage of1.5V) is around the middle, which is “32760.”

As obvious from FIG. 13, in the case of normal press/release, the outputvoltage starts declining immediately after the end of press. Then, thedecline rate increases as the ADC value increases. Thus, if the releasethreshold vector is set in a fixed manner, erroneous determination ofrelease may occur.

Thus, in the electronic device according to the third embodiment of thepresent invention, in the electronic device 1 according to the firstembodiment, after the tactile sensation providing unit 30 provides atactile sensation, further, the press/release determination unit 51changes the threshold vector based on the maximum value (initial localmaximum value) of obtained ADC value. In detail, a tactile sensation isprovided by the piezoelectric element 31 when pressed, further,discharge processing of the piezoelectric element 31 is performed, thenwhen detection of output voltage from the piezoelectric element 31 isstarted, the press/release determination unit 51 changes the absolutevalue of release threshold vector according to the maximum value of theobtained ADC value, such that the larger the maximum value, the largerthe change.

FIG. 14 is a diagram illustrating an example of a source code of thechanged portion of the release threshold vector by the press/releasedetermination unit 51 in this case. The variables illustrated in FIG. 9are as follows:

-   -   “peek_ave_power”: The maximum value of ADC value    -   “base_ad_value”: Reference value of ADC value    -   “rel_vect”: Absolute value of release threshold vector;    -   “down_thresh”: The number of consecutive times the minus        direction vector is detected to be determined as release.    -   “ave_power”: ADC value obtained when the present vector is        determined;

Note that, in FIG. 14, calculation method of release threshold vectorvaries depending on the maximum value, reference value and the like ofADC value.

As described above, according to the electronic device 1 of the presentembodiment, after a tactile sensation for press is provided, theabsolute value of the release threshold vector is changed based on themaximum value of obtained ADC value, thus, in addition to the effect bythe first embodiment, even if the ADC value declines immediately afterthe end of press, the immediate decline may be prevented from beingerroneously determined as “release.” Therefore, a tactile sensationproviding function may be improved and a tactile sensation may beprovided appropriately without causing any discomfort to the operator.

Note that the present invention is not limited to the above describedembodiment, and variety of modifications and changes may be made. Forexample, in comparison of ADC value and threshold voltage by thepress/release determination unit 51, the ADC value satisfies the pressthreshold voltage may be when the ADC value reaches the press thresholdvoltage, when the ADC value exceeds the press threshold voltage or whenthe press threshold voltage is detected by the press/releasedetermination unit 51. In addition, the ADC value satisfies the releasethreshold voltage may be when the ADC value reaches the releasethreshold voltage, when the ADC value falls below the release thresholdvoltage, or when the release threshold voltage is detected by thepress/release determination unit 51. Similarly, the vector satisfies thethreshold vector may be when the absolute value of the vector reachesthe absolute value of the threshold vector, when the absolute value ofthe vector exceeds the absolute value of the threshold vector, or whenthe threshold vector is calculated by the press/release determinationunit 51.

Then, in the above described embodiment, both press and release aredetermined. However, the electronic device may be configured todetermine either press or release to provide a tactile sensation.Furthermore, press/release determination processing may be performedbased on a comparison between the vector calculated from the ADC valueand a predetermined determination threshold vector, without using athreshold voltage.

In addition, the panel 10 and the display 20 may be integrated into adevice that includes a common substrate having both of these functions.An example of such device is a liquid crystal panel having a matrix ofpixel electrodes, with a plurality of photoelectric conversion elements,such as photodiodes, regularly mixed therein. In such device, images aredisplayed by a liquid crystal panel structure, and on the other hand,the backlight for the liquid crystal display is reflected by the tip ofpen that contacts with the desired position on the surface of the panelfor input, and the light reflection thereof is received by theperipheral photoelectric conversion elements, thereby the contactposition may be detected.

Furthermore, in the above described embodiment, the panel 10 is used todetect contact to the operation face 10 a, and it is also possible todetermine that contact has been made when the output voltage from thepiezoelectric element 31 satisfies the reference voltage correspondingto a predetermined press load.

In addition, the press detection element that obtains data based onpress against the panel 10 may be provided independently, withoutsharing the piezoelectric element with the tactile sensation providingelement. Therefore, in this case, as a press detection element, a vectorof output voltage may be detected by using a piezoelectric element and astrain gauge, and a vector of contact area of the panel 10 may also bedetected. Then, as a tactile sensation providing element, a vibrationmotor (eccentric motor) may be used and, by vibrating the motor, thetouch face 10 a of the panel 10 may be vibrated indirectly.

Furthermore, in the above described embodiments, the reference value(reference voltage) is 1.5V or 1.6V, however, in the present invention,the reference value is not limited thereto, and may be 0V. In addition,in the above described embodiments, as the data based on press, ADCvalue, which is digital data, is used. However, in the presentinvention, the data based on press is not limited thereto, and may be anoutput voltage, which is analog data. Then, all of the processingaccording to the present invention, including data threshold, may beprocessed by analog data.

REFERENCE SIGNS LIST

-   -   1 Electronic device    -   10 Panel    -   20 Display    -   30 Tactile sensation providing unit    -   31 Piezoelectric element    -   40 Memory unit    -   50 Controller    -   51 Press/release determination unit    -   52 Tactile sensation control unit    -   61,62 Changeover switch    -   71,72 Capacitor    -   80 ADC (analog digital converter)    -   521,522 Step-up converter    -   523 Positive electrode voltage control circuit    -   524 Negative electrode voltage control circuit

The invention claimed is:
 1. An electronic device, comprising: a tactilesensation providing unit configured to provide a tactile sensation to acontact object being in contact with a panel; and a controllerconfigured to control the tactile sensation providing unit on the basisof an amount of change of voltage based on press to the panel incomparison with a threshold, wherein the threshold is changed after thetactile sensation providing unit provides the tactile sensationaccording to a position of contact of the contact object to the panel.2. An electronic device, comprising: a tactile sensation providing unitconfigured to provide a tactile sensation to a contact object being incontact with a panel; and a controller configured to control the tactilesensation providing unit on the basis of an amount of change of databased on press to the panel in comparison with a threshold, wherein thethreshold is changed after the tactile sensation providing unit providesthe tactile sensation, wherein the controller controls the tactilesensation providing unit based on a temporal amount of change of thedata and a threshold of amount of change.
 3. An electronic device,comprising: a tactile sensation providing unit configured to provide atactile sensation to a contact object being in contact with a panel; anda controller configured to control the tactile sensation providing uniton the basis of an amount of change of data based on press to the panel,wherein the controller calculates a vector indicating the temporalamount of change of the data and a polarity of the amount of change, andbased on the vector and a threshold vector, controls the tactilesensation providing unit.
 4. The electronic device according to claim 3,wherein the threshold vector has a press threshold vector in which thevector corresponds to a plus direction vector indicating an increase inthe amount of change and a release threshold vector in which the vectorcorresponds to a minus direction vector indicating a decrease in theamount of change.
 5. The electronic device according to claim 4, whereinan absolute value of the press threshold vector is larger than anabsolute value of the release threshold vector.
 6. The electronic deviceaccording to claim 2, wherein the controller controls the tactilesensation providing unit based further on the data and a data thresholdcorresponding to the data.
 7. A control method of an electronic deviceconfigured to control a tactile sensation providing unit that provides atactile sensation to a contact object being in contact with a panel by acontroller, the method comprising: controlling the tactile sensationproviding unit based on an amount of change of voltage based on press tothe panel in comparison with a threshold, wherein the threshold ischanged after the tactile sensation providing unit provides the tactilesensation according to a position of contact of the contact object tothe panel.
 8. An electronic device, comprising: a tactile sensationproviding unit configured to provide a tactile sensation to a contactobject being in contact with a panel; and a controller configured tocontrol the tactile sensation providing unit based on an amount ofchange of data based on press to the panel and a threshold of amount ofchange, wherein after the tactile sensation providing unit provides atactile sensation, the controller changes the threshold of amount ofchange.
 9. The electronic device according to claim 8, wherein thecontroller decreases, after the tactile sensation providing unitprovides a tactile sensation, the threshold of amount of change withtime.
 10. The electronic device according to claim 8, wherein thecontroller increases, after the tactile sensation providing unitprovides a tactile sensation, the threshold of amount of change withtime.
 11. The electronic device according to claim 8, wherein thecontroller changes, after the tactile sensation providing unit providesa tactile sensation, the threshold of amount of change depending on aposition of contact of the contact object to the panel.
 12. A controlmethod of an electronic device configured to control a tactile sensationproviding unit that provides a tactile sensation to a contact objectbeing in contact with a panel based on an amount of change of data basedon press to the panel and a threshold of amount of change, including astep of after the tactile sensation providing unit provides a tactilesensation, changing the threshold of amount of change.
 13. An electronicdevice comprising: a tactile sensation providing unit configured toprovide a tactile sensation to a contact object being in contact with apanel; and a controller configured to control the tactile sensationproviding unit based on an amount of change of data based on press tothe panel and a threshold of amount of change, wherein the controllerchanges, after the tactile sensation providing unit provides a tactilesensation, the threshold of amount of change based on a maximum value ofthe data based on press to the panel.
 14. A control method of anelectronic device configured to control a tactile sensation providingunit that provides a tactile sensation to a contact object being incontact with a panel based on an amount of change of data based on pressto the panel and a threshold of amount of change, including a step of;after the tactile sensation providing unit provides a tactile sensation,changing the threshold of amount of change based on a maximum value ofthe data based on press to the panel.